I disagree they were doing nothing wrong. With the benefit of hindsight, they were going faster than they could deal with the conditions. This may be understandable or even excusable, but let's not turn this forum into another haven of stories of poor downtrodden motorists who have nothing to do with the damage they do!
Legality is disconnected from safety and reason on escooters in the UK. I'm not willing to condemn them merely because our MPs have been shirking.
Legallity has a lot to do with it. If you were hit by a motor vehicle that shouldn't have been on the road(no VED, MOT or insurance) in the first place, you have somewhere to turn. With these, there's no-where except the person in charge at the time.
You appear to feel that they were going too fast for conditions at the time. This makes them responsible for the action of person in charge of the hoverboard at the time, in your eyes. Despite the latter not being road legal.
Driver(and vehicle) were going little over walking pace, having just passed one group of kids playing in/on the road. Their playground.
I was there when it happened, were you?